The Data-Over-Cable Service Interface Specification (DOCSIS) was established by cable television network operators to facilitate transporting data traffic, primarily Internet traffic, over existing community antenna television (CATV) networks. In addition to transporting data traffic, as well as television content signals over a CATV network, multiple services operators (MSO) also use their CATV network infrastructure for carrying voice, video on demand (VoD) and video conferencing traffic signals, among other types.
These networks typically use internet protocol (IP) addressing schemes to address the various devices on the network. IPv6 specifies that when a new device enters the network, it transmits a node solicitation (NS) message containing the tentative address. If there are any devices on the network that have already claimed the tentative address, those devices respond with a node advertisement (NA) message.
In various architectures, this process is more difficult. For example, in cable networks, the devices do not listen to upstream channels, and therefore would not receive the NS message. However, in such systems, a headend/central office device (e.g., a cable modem termination system (CMTS) or digital subscriber line (DSL) access multiplexer (DSLAM)) can provide a duplicate address detection (DAD) proxy operable to provide NA messages for the devices connected to it.